Synthesis and Characterization of the Thiazolidinone and / or Thiourea substituted Amine Complexes of Cu ( II )

Mixed ligand complexes of copper (II), involving either Mercaptyl thiazolidinone (1) [2-(2hydroxy benzoyl)-3-N-(2-mercaptyl)-1-Thiazolidin-4-one] or Pyridine thiazolidinone (2) [ 2-(2hydroxy benzoyl-3-N-(2-Pyridinyl)-1-Thiazolidin-4-one] alone and along with Thiourea were synthesized by partial or complete replacement of the strongly coordinated ammonia of ammine complex. All the products have been characterized by elemental analysis, molar conductance, magnetic susceptibility, IR and electronic spectral measurements for their bonding and structures.


Materials and methods
Thiazolidinones (1) and (2) were prepared by known methods [4] of cyclocondensation of respective ketoanils with thioglycolic acid and purified by recrystallization.Ammine complex Cu(NH 3 ) 4 ]Cl 2 was prepared and purified by King's methods [5] .Metal Chloride and other chemicals (Aldrich, Qualigen and BDH) were used as supplied except solvents which were used after distillation.

Preparation of Complexes
Complexes resulting from partial replacement of coordinated ammonia by (1) or (2) alone and along with thiourea were prepared by mixing ethanoic solutions of ligands (0.1 mol each) with aqueous ethanoic (70%) solutions of ammine complexes (0.1 mol) in presence of NH 3 (5 cm 3 ).afraction of ligand (1) and thiourea substituted ammine complexes of Cu (II) precipitated immediately or after refluxing the reaction mixture (4-6hrs) .The products were washed with EtOH/ Me 2 CO and dried in hot air oven at 80°C; b-fraction isolated from filtrates on concentration and crystallization was washed with EtOH/AcOH-Toluene(3:1 v/v) Et 2 O and dried at 100°C Ligand (II) substituted ammine complexes of Cu(II) crystallized from their reaction mixtures after their 6-12 hrs refluxing from the reaction mixture containing (2)

Resolution of binary complexes
Chromatography was undertaken in a column (50cm length, 2cm diameter) containing silica gel (50-100 mesh, BDH) in AcOH-C 6 H 6 (2:1 v/ v).The binary products were dissolved in dimethylsulphoxide and loaded in the column, and the fast moving component eluted.The slow moving component was eluted with an appropriate solvent.Eluates were evaporated to dryness under reduced pressure.

Analysis and Physical Measurements
C , H and N analysis were done on Varioel-III Element-R.Melting points determined in open glass capillaries were uncorrected, infrared spectra were recorded on Thermo Nicolet Nexus FT-IR spectrometer in Nujol whereas reflectance spectra were recorded on a Carl-Zeiss VSU-2P spectrophotometer in MgO.Conductometric measurements on standard solutions of complexes in DMSO were made on Toshniwal Conductivity Bridge using a dip-type cell.Magnetic susceptibilities for solids were measured in vibrational magnetometer.Molecular weights were determined by micro Rast's method [6] using Camphor solvent.

RESULTS AND DISCUSSION
Analysis and molecular weights data are in conformity of proposed molecular formulae.Silver nitrate test revealed non-electrolytic nature of complexes.
IR spectrum of (1) together with ammonia and thiourea exhibits frequencies of C-N (cyclic), C-S-C (cyclic) and SH groups at 1600 cm -1 690cm -1 and 2670cm -1 respectively.Considerable lowering in C-N(cyclic) frequency and disappearance of SH band in complexes led to the inference that (1) is coordinated with metal ions through its thiazolidinone ring nitrogen and deprotonated mercaptyl group.New low frequency peaks corresponding to M-N and M-S stretches appeared in the spectra of complexes supported the participation of these groups in coordination.Ligand (2) displays C = O(cyclic) and C=N(cyclic) vibrations at 1600 cm -1 and 1590cm -1 respectively.In the complexes obtained by partial or complete substitution of ammonia by (2) alone or along with SCN 2 H 4 , thiazolidinone ring carbonyl group peak disappeared and pyridine ring C=N group frequency lowered considerably.This suggests coordination of thiazolidinone ring carbonyl oxygen after its enolization and pyridine ring nitrogen.Two new low frequency bands corresponding to M-O and M-N stretches confirm this inference.In the products obtained by partial substitution of ammonia by (1) or (2) an additional band of M-N is observed.If two nitrogens are coordinated one is from thiazolidinone ring or pyridine ring and other should be from ammonia.The low symmetrical deformation (ca.1608 cm -1 ) and rocking(ca.842 cm -1 ) vibrations of coordinated ammonia confirm this.In the IR Coordination of monodentate chlorine is indicated by M-Cl band occurring in 300 cm -1 -320 cm -1 region whereas chlorine bridged polynuclear structures are supported by either a well-defined M-Cl-M peak or a broad peak arising by mixing of closely spaced M-Cl peak., indicate its square-planar geometry.All other copper (II) complexes displaying one or two broad bands in 12516-15385 cm -1 range and other two or three bands in 16367-24510 cm -1 region indicate [10] their distorted octahedral stereochemistry involving 2 T 2g  2 E g transitions; the 2 E g state being susceptible to John-Teller distortion may account for the broad peak structure.